Abstract: The reversible logical circuits, due to their economised power consumption in comparison with their counterparts with binary circuits, have become a major issue of study. A reversible circuit with equal parity of inputs and outputs is considered as a parity preserving circuit. In such circuits, any fault effecting only one logical signal, is detectable at the main outputs. A new 5 × 5 parity preserving reversible block called RRH is proposed which would operate as a half adder/subtractor and a full adder/subtractor. The outcome of comparisons indicates that this proposed block outperforms its counterparts with respect to the number of constant inputs and garbage outputs, quantum cost and circuit dimensions.